It is well known that the conventional combine harvester includes one or more sieve elements at the rear of the body for separating seeds from the chaff. Generally two such elements are used one above the other so that two subsequent separation steps are effected.
In many cases the upper sieve element is known as the chaffer and the lower sieve element is known as the sieve. The elements are however of very similar construction and the present invention is directed to either of these elements. Thus the term "sieve" used in this specification is intended to relate to either or both of the elements or to any similar construction of a combine harvester which provides a series of openings for acting as a sieve to separate seeds from chaff.
Generally the construction comprises a plurality of parallel longitudinal rails. Across the rails are provided a plurality of longitudinally spaced parallel wires which pass through aligned holes in the rails. On each wire is attached a plurality of separate louver sections which are carried by the wire and provide fingers extending forwardly from the wire. The fingers of each wire co-operate with the louver sections of the next wire to form openings through which air can be directed from below by a fan to all areas of the sieve construction and through which seeds can pass under gravity for collection on the sieve underneath or for collection in a suitable collection system well known to one skilled in the art.
The wires are connected to the louver sections by welding so that each louver section is held at a predetermined angle relative to the wire. The wires are round in cross section and simply pass through round hole stitching in the louver or lay flat against the louver. The wires pass through simple holes in the rails and are supported thereby. Rotation of the wires relative to the rails is effected only for adjustment of the angle of the louvers and this is done very infrequently and in some cases as infrequently as a few times during harvest depending upon the crop material to be separated. There is therefore no rotation of the wires relative to the rails which would effect wear of the wires and therefore the rails simply have a hole through which the wire passes without generally the necessity for any kind of bearing arrangement.
The adjustment movement is effected by a longitudinal rod parallel to the rails which is moved back and forth by an adjustment lever and acts to push a portion of the wire forwardly and backwardly to twist that portion about a longitudinal axis of a main portion of the wire.
The welding of the louver sections to the wire provides a substantially rigid construction and holds the rails at the required spaced positions due to the engagement of the ends of the louver sections with the sides of the rails.
This arrangement has been manufactured for many years and is adopted in substantially all combine harvesters.
One arrangement manufactured by HARVEST AIR in Australia has attempted to improve the sieve construction by providing in each rail a slot from the top edge downwardly and the wires are inserted into plastic hanger members at each rail which are shaped to fit into the slot. This arrangement allows the wires to be pulled vertically upwardly from the rails for separation therefrom. The plastic hangers provide some resilience of the wires relative to the rails. The plastic hangers are fixed in the rails and the wires are circular so they rotate within the holes in the plastic hanger. This arrangement allows one wire and its attached louvers to be lifted from the rails and replaced in the event of damage or wear. However this arrangement is not widely used and is not used in North America.
However, apart from the little known Australian arrangement above, all of these constructions have the disadvantage that it is very difficult to disassemble the sieve construction once completed so that it is impractical to replace any elements of the sieve construction and once damaged or worn the complete sieve construction is abandoned and replaced by a new assembly. In the current climate of recycling and reuse, this is of course unacceptable.
Yet further the sieve construction in view of its welded formation is difficult to provide modifications which would provide a different shape of a number of the louvers so that the sieve can be tailored for particular crops or particular conditions. The current manufacturers take the position that the sieve is commercially available at a relatively inexpensive price and therefore the customer should take the construction that is available.